

When Susan returns the Daleks discover the second drug supply, but allow the humans to treat themselves with it.

Alydon gives Susan a second container of anti-radiation drugs to use if the Daleks fail to keep their promise. Reaching Tardis Susan collects the drugs and then encounters Alydon, leader of the Thals, a species that fought the Daleks in an atomic war centuries previously. Susan goes, being the only one still strong enough to undertake the task. If the humans bring the drugs they found to them, they will allow them enough to treat themselves. Hearing the captives discussing the drugs, the Daleks make a proposal to them. They wish to leave so that they can destroy all other life and claim the planet for themselves. They are trapped inside their metal casings, and within the city, by the radiation. While covertly observing the captives, the Daleks discuss their own plight. Who then realises that the group have contracted radiation sickness, and that the drugs they discovered earlier may be their only hope of survival. Once in the city they are captured by cyborg creatures which refer to themselves as " Daleks", who seize the fluid link for examination.

Who fakes a leak in a fluid link, a vital component of Tardis, to ensure that the group will go to the city to search for the mercury supposedly needed to refill the component. They also find a small container of drugs which they take aboard Tardis. While exploring, the travellers see a city in the distance. Who's latest invention, a time and space machine called Tardis. Who, his granddaughters Susan and Barbara, and Barbara's boyfriend Ian are accidentally transported to another planet by Dr.
